Positive

In common usage positive is sometimes used in affirmation, as a synonym for "yes" or to express "certainty".

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In mathematics, a number is called positive if its value is greater than zero. See negative and non-negative numbers.
In functional analysis, a bounded linear operator is positive if its spectrum consists of positive real numbers.
In physics, one distinguishes positive and negative electric charges.
In optics, converging lenses are also called positive lenses.
In linguistics, positive is the form of an adjective or adverb on which comparative and superlative are formed.
If a scientific test for a condition or hypothesis is applied, the outcome is termed positive if the condition is detected or the hypothesis confirmed (or, rather, not disproved).
If a medical test for a certain disease is applied, the outcome is termed positive if the disease is detected.
In the humanities and social sciences, a theory is called positive if it aims to describe what is the case as opposed to what ought to be the case. See positive science.
In the philosophy of law and other areas, a right or freedom may be positive (see negative and positive rights).
In philosophy, positivism is the name for theories which aim to be based on facts alone, eschewing metaphysics and religion.
In astrology, positive is a term commonly used to described the supposedly extroverted personalities of the fire and air signs.
In policy debate, affirmative is the team which affirms the resolution.

the process of replacing negative thoughts with positive ones is referred to as